Fox News Weather Center

Cold Storm to Bring White Thanksgiving to Portions of Western US

Rain, snow and cold air will return to the Northwestern states into Thanksgiving.

A storm system will dive southward along the West Coast into Tuesday before tracking eastward across the Rockies into Thanksgiving Day.

The strength and track of this storm system will determine which locations will receive the heaviest snowfall on the cold side of this system.

The amount of moisture available with this system will be much less than the previous storms this month across the Pacific Northwest. While much of the lower elevations will deal with periods of rain, the threat for flash flooding will be low.

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Much of the precipitation along the Interstate 5 corridor from Seattle to Portland, Oregon, will be in the form of rain into Tuesday.

A steady snow will blanket the Cascades. Significant snowfall will also occur across the Bitterroot Mountains of Idaho and western Montana as well as the Sierra Nevada.

As this system tracks south and east this week, a shot of cold air from Canada will dive across the region behind this storm. This will allow snowflakes to make an appearance across some of the lower elevations for the first time this season.

"Snowflakes will mainly just make an appearance in Seattle and Portland, Oregon, on Monday night," AccuWeather Senior Meteorologist Kristina Pydynowski said. "The low elevations east of the Cascades have the better opportunity to receive accumulating snow on Tuesday into Wednesday, especially in eastern Oregon."

"Snow in Seattle during late November in not all that unusual," AccuWeather Meteorologist Michael Doll said.

"Between 2 and 3 inches of snow fell in the city on Nov. 22, 2010."

Those traveling for Thanksgiving across the Northwest through Tuesday should give yourself extra time to reach your destination as roads will be wet or perhaps snowcovered and icy.

Anyone waiting to travel on Wednesday should see improving conditions across the Pacific Northwest as the storm will set its sights across the northern and central Rockies into Nevada. Those traveling in these areas may want to consider leaving before Wednesday before the storm approaches.

"The snow will focus on the corridor from Montana and Wyoming to eastern Oregon and the Sierra on Wednesday," Pydynowski said.

Plowable snow could accumulate across the northern Rockies including Billings, Montana; Casper, Wyoming; and Salt Lake City on Wednesday into Wednesday night.

The best opportunity for snowflakes to make an appearance in Boise, Idaho, is on Wednesday into Wednesday night. Snow is expected to accumulate only on non-paved surfaces.

Overnight low temperatures will plunge near or below freezing across much of the Western states into Thanksgiving. Locations along the Pacific Coast will remain above freezing.

The last time Seattle reached the freezing mark was in early March.

Anyone traveling after dark will need to use caution as wet roads could start to freeze.

Daytime high temperatures across much of the northern and central Rockies will fail to reach the freezing mark on Wednesday and Thursday. This will not allow all of the snow that falls this week to melt before the Thanksgiving holiday.

Those flying for the holiday across the West should keep checking your airline for any possible delays or cancellations or consider booking a flight before the storm arrives.

Snow showers could continue to occur across portions of the central Rockies on Thanksgiving Day.